Technological infrastructure, sleep, and rest-activity patterns in a Kaqchikel Maya community.

Sleep duration, quality, and rest-activity pattern-a measure for inferring circadian rhythm-are influenced by multiple factors including access to electricity. Recent findings suggest that the safety and comfort afforded by technology may improve sleep but negatively impact rest-activity stability. According to the circadian entrainment hypothesis, increased access to electric lighting should lead to weaker and less uniform circadian rhythms, measured by stability of rest-activity patterns. Here, we investigate sleep in a Maya community in Guatemala who are in a transitional stage of industrialization. We predicted that (i) sleep will be shorter and less efficient in this population than in industrial settings, and that (ii) rest-activity patterns will be weaker and less stable than in contexts with greater exposure to the natural environment and stronger and more stable than in settings more buffered by technologic infrastructure. Our results were mixed. Compared to more industrialized settings, in our study population sleep was 4.87% less efficient (78.39% vs 83.26%). We found no significant difference in sleep duration. Rest-activity patterns were more uniform and less variable than in industrial settings (interdaily stability = 0.58 vs 0.43; intradaily variability = 0.53 vs 0.60). Our results suggest that industrialization does not inherently reduce characteristics of sleep quality; instead, the safety and comfort afforded by technological development may improve sleep, and an intermediate degree of environmental exposure and technological buffering may support circadian rhythm strength and stability.

Social and Biological Transgenerational Underpinnings of Adolescent Pregnancy.

Adolescent pregnancy (occurring < age 20) is considered a public health problem that creates and perpetuates inequities, affecting not only women, but societies as a whole globally. The efficacy of current approaches to reduce its prevalence is limited. Most existing interventions focus on outcomes without identifying or addressing upstream social and biological causes. Current rhetoric revolves around the need to change girls' individual behaviours during adolescence and puberty. Yet, emerging evidence suggests risk for adolescent pregnancy may be influenced by exposures taking place much earlier during development, starting as early as gametogenesis. Furthermore, pregnancy risks are determined by complex interactions between socio-structural and ecological factors including housing and food security, family structure, and gender-based power dynamics. To explore these interactions, we merge three complimentary theoretical frameworks: "Eco-Social", "Life History" and "Developmental Origins of Health and Disease". We use our new lens to discuss social and biological determinants of two key developmental milestones associated with age at first birth: age at girls' first menstrual bleed (menarche) and age at first sexual intercourse (coitarche). Our review of the literature suggests that promoting stable and safe environments starting at conception (including improving economic and social equity, in addition to gender-based power dynamics) is paramount to effectively curbing adolescent pregnancy rates. Adolescent pregnancy exacerbates and perpetuates social inequities within and across generations. As such, reducing it should be considered a key priority for public health and social change agenda.

The metabolic cost of avian egg formation: possible impact of yolk precursor production?

Little is known about the energy costs of egg production in birds. We showed in previous papers that, during egg production, European starlings (Sturnus vulgaris) undergo a 22% increase in resting metabolic rate (RMR) and that the maintenance and activity costs of the oviduct are responsible for 18% of the variation in elevated laying RMR. Therefore, other energy-consuming physiological mechanisms must be responsible for the remaining unexplained variation in elevated laying RMR. Yolk precursor [vitellogenin (VTG) and very-low-density lipoprotein (VLDL)] production is likely to be costly because it signifies a marked increase in the biosynthetic activity of the liver. We documented the pattern of yolk precursor production in response to daily injections of 17beta-estradiol (E2) in zebra finches (Taeniopygia guttata). Based on this pattern we carried out an experiment in order to evaluate the metabolic costs of producing VTG and VLDL. Our E2 treatment resulted in a significant increase in plasma VTG and VLDL levels within the natural breeding range for the species. Although RMR was measured during the period of active hepatic yolk precursor production, it did not differ significantly within individuals in response to the treatment or when comparing E2-treated birds with sham-injected birds. This could mean that yolk precursor production represents low energy investment. However, we discuss these results in light of possible adjustments between organs that could result in energy compensation.